Heating and Insulation

An extremely important consideration in building a home, often overlooked by the inexperienced builder, is insulation, as well as siting and design considerations that minimize heat loss in winter, heat gain in summer.

Before building anything, we urge you to get available local climatological information and read sections of books that explain insulation. (Check the library.) In Kern’s The Owner Built Home there is excellent information on siting, heating, cooling, planting design and building climatology. In Wood Frame House Construction there is a good chapter on thermal insulation and vapor barriers. (See bibliography.)

We cannot cover the subject adequately here, and there is no substitute for local knowledge, but following are a few principles that may be helpful:

House orientation is very important. If windows face the hot summer sun, there will be high heat gain. (In one dome with a great quantity of windows facing the sun, temperatures got over 140°, and several phonograph records actually melted—one of them was It’s a Beautiful Day.) Conversely, windows on a wall facing cold winter winds will admit cold. And doors and windows should be sealed well (felt strips) to keep out winds.

There are three principles of heat transfer: convection, conduction, and radiation. Convection refers to the currents in the air that transfer heat through unsealed spaces; conduction is heat transferring through solid surfaces; radiation is direct transfer of heat through the air. All three of these principles play a part in heat loss and gain in buildings, and the different methods of insulating involve one or more of the three.

An example of stopping loss via convection would be fire blocking in stud walls that stops drafts (and fire danger), or fill insulation. An example of dealing with conduction would be layer(s) of insulation with air spaces in between. Finally, radiation heat loss is best stopped by a bright metal surface.

In double-wall construction (studs with exterior, interior sheathing) the most common and cheapest insulation is the flexible fiberglass with aluminum backing and built-in vapor barriers. This is stapled in between the studs; the aluminum facing in, to be effective, with an air space between the aluminum and interior wall surface.

(A principle to remember with aluminum is that, for it to reflect heat by radiation, there must be air space; otherwise it will transfer heat by conduction.)

Floors can also be insulated with roll fiberglass. Exposed ceilings can be insulated by rigid insulation on top of the roof sheathing. (0.75" rigid insulation is twice as effective as the half-inch.)

In colder climates, sprayed polyurethane foam is a consideration. It is the best insulation but expensive and extremely dangerous if it catches fire, as it burns explosively and emits poisonous gases. If used, it should be protected with a fireproof wall inside, such as sheet rock or plaster.

Another source of heat loss is imperfect combustion in the burner of the house heater. A brick or stone fireplace loses a great deal of heat, although a heatilator unit will improve this considerably. If a metal flue is used, the more of it that is inside, the more heat will remain inside, rather than being lost outside. (See The Last Whole Earth Catalog for fireplace info.)

Low-ceilinged rooms are obviously easier to heat. In cold climates, double-glazing (must be sealed) is used to insulate windows.

In 1973, it took an average of $90 worth of propane to heat a three-bedroom house in a cold area in Northern California, and many people in the area were switching to diesel heating. Fuel is going to get scarcer, so if you are building, insulate well; the extra money you spend will be paid back within a few winters.